1. Field of the Invention
The present invention relates to an implarnable intraluminal device. More specifically, the present invention relates to an implantable intraluminal device which is particularly useful for repairing or serving as a conduit for vessels narrowed or occluded by disease or for use in other body passageways requiring reinforcement or the like. Further, devices are disclosed in the present invention that can trap particulate that is loosened during interventional procedures such as stent or stent-graft placement, angioplasty, atherectomy, etc.
2. Description of Background Art
Intraluminal devices or, more specifically, endovascular prostheses, are known for treating stenosis, stricture, aneurysm conditions and the like. Often these devices are implanted via LIS (Least Invasive Surgery); whereby a small percutaneous access into the vessel is accomplished (usually remote to the diseased area). Alternatively, they are installed via an `open surgery` approach. Advantages of the LIS approach (over conventional surgery) are significant from a cost as well as a patient care and recovery point of view. Intraluminal scaffolding devices such as stents are often used in combination with grafts and vice versa. The graft is usually, but not always a textile/fabric type device that is used to cover a greater area of the scaffolding as well as aid in neo-intimal formation after placement. Further, the two (stents and grafts) are often designed into one device called a stent-graft.
Each year about half a million Americans suffer a stroke in which obstruction or hemorrhage impairs the crucial flow of blood to the brain. About 150,000 of these stroke victims die, making stroke the third leading cause of death after heart disease and cancer, and many more suffer permanent disability. According to the American Heart Association the cost of treating stroke exceeds $25 billion a year.
Currently, approximately 180,000 Americans undergo a preventative operation to clear carotid arteries that carry blood to the brain. The operation, known as Carotid Endarterectomy (surgical removal of plaque from the carotid artery), usually requires patients to stay in the hospital a few days, with typically a few weeks recovery time. This surgical procedure is increasing at an annual rate of greater than 20%.
A debate has arisen between vascular surgeons and "interventional" cardiologists and radiologists concerning the advantages of using of stents and/or stent-grafts to treat occluded carotid arteries compared with surgery. Stroke prevention operations/surgeries like endarterectomies are performed by vascular surgeons in the United States at a cost of about $1.5 billion per year. Efforts to use small stents in the brain to open and maintain patency in clogged arteries have triggered a fierce debate comparing the safety and efficacy of the medical techniques. Interventionalists claim that the scaffolding accomplished with stents is easier on the patient and the patient's pocketbook. Surgeons, on the other hand, are skeptical of stenting in the carotid because of the potential for neurological complications as well as the potential for the stent to `recoil` (return to a smaller diameter than when originally placed) some time after initial placement.
Various strategies have been devised and developed for vascular intervention in the treatment of Chronic Occlusive Disease (COD). Much of the critical occlusive disease occurs at junctions (bifurcations) in the vasculature. Of particular interest are occluded carotid arteries and other bifurcated vasculature junctures.
A recent study funded by the NIH indicates the incidence of stroke can be reduced by 55% if the occluded carotid is treated by surgical intervention. This surgical procedure sometimes allow minute pieces of plaque or blood clot (emboli) to travel into the brain causing at least temporary neurological damage, and often stroke or permanent neurological defects.
Various devices have been devised and used to dispense thrombolytic agents to the occluded vasculature and/or physically disrupt and dislodge the occluding thrombus. One such catheter, described in U.S. Pat. Nos. 5,498,236, 5,380,273, and 5,713,848 by the present inventor was developed to penetrate and cross occluded portions within the vasculature, deploy an occlusion device distal to the occlusion to stop emboli from iatrogenic damage while clearing the occlusion/blockage. Although such catheters are adequate for removing occluding tissue in a vessel lumen, restenosis occurs unless balloon angioplasty or some sort of scaffolding is left in place to prop the vessel open (e.g. stent or stent-graft). Scaffolding is becoming a preferred treatment, usually with balloon angioplasty (or sometimes without) because balloon angioplasty when used without some type of scaffolding has a tendency to have a temporary result.
Femoral artery access allows the interventionalist an easy, safe and less costly approach to treat carotid stenosis with the least invasive trauma to the patient (other access is used as well). However, the need arises for a stent that can be deployed at a vascular "bifurcation" which does not occlude the side tributary (or side branch) at the bifurcation and still provide sufficient radial force to keep the vessel sufficiently open. In other words, a multi-porous or bifurcated stent or stent-graft that provides scaffolding at the vascular bifurcation and still allows blood to flow in the main vessel as well as into the bifurcated tributary is desirable.
The prior art regarding scaffolding or `propping open` of closed or stenotic vessels is extensive. Stents or stent-grafts for scaffolding singular lumens (without bifurcations) are numerous. Stents in the past decade have been one of the most prominent technologies dealing with occlusive vascular disease. Additionally stents or stent-grafts for non-vascular occlusions such as urological, esophageal, biliary, etc. are prevalent as well. U.S. Pat. No. 5,383,925 by Schmitt et al describe a three dimensional braided soft tissue prostheses. In and of itself; this invention has similarities to the present invention because the present invention also discloses braided prostheses (as well as a non-braided prosthesis). However, Schmitt et al does not address the subject of tributaries and bifurcations. Similarly, U.S. Pat. No. 5,366,505 by Anderson et al describe a tubular medical prosthesis with knitted filaments with openings in between the filaments. This patent also does not address scaffolding of bifurcations. The stent or scaffolding intellectual property of this type that do not address stenting of bifurcations is extensive and will not be further addressed in this patent.
Conversely, endovascular support devices that address this scaffolding or stenting of bifurcations although much less common than the aforementioned non-bifurcated stents or stent-grafts are also prevalent in the market of stents as well in the patent theatre. For example U.S. Pat. No. 5,718,724 by Goicoechea et al describe a bifurcated endoluminal prosthesis and method of installing the device, whereby the stent is configured into a one or two part Y configuration. In an analogous U.S. Pat. No. 5,632,763 by Glastra et al; the bifurcated stent in this patent is also an Y shaped scaffold. In these and similar Y shaped/configured bifurcated stents, the stent is designed to be placed in the entire bifurcation or Y. This enables scaffolding of the entire junction of all three tributaries.
However, there are situations where only the main vessel of the tributary is required to be stented. Such appears to be the case of stenting the bifurcation of the carotid artery. Thousands of linear (as opposed to Y stents) stents have been placed without FDA approval in the U.S. in this bifurcated carotid area. In these cases, a stent is placed into the common carotid artery and further into the internal carotid artery. The stent is placed across the external carotid artery. These stents have walls with a very `open` structure in that they are braided stents but have large enough areas to allow blood to flow through the stent wall and into the external carotid artery or other side branch These numerous implantations have been reported without significant complications however at the time of this invention, prospective and long-term studies have not been completed. Blood flow from the common carotid artery and into the internal carotid artery appears to be more important due to the fact that the internal carotid artery feeds blood into the middle cerebral artery and other arteries of the brain. However, blood flow into the external artery is still important and has to pass through the stent wall. This is known as `stent jail` because the blood has to pass through the weaves/filaments of the stent. Because of this phenomenon, only stents with large openings between the filaments of the stent can be used. This creates another problem in that there is a direct correlation between the openings between the filaments (pics per inch) and the outward radial force that can be transmitted to the vessel wall. As this open space increases, the outward radial force of the stent decreases. Conversely as the openings decrease in size, the radial force increases. Hence it is the object of the present invention to obviate that disadvantage by designing a multi-porous stent for bifurcations that allow a sufficient outward radial force, but still allows flow into the tributary or side branch U.S. Pat. No. 5,607,444 by Lam describes an ostial stent for bifurcations that is different than the Y configuration in that it the main tubular body of the stent is seated into the side branch and has a flaring end that is attached into the main vessel thereby not obstructing flow of the main branch This design may be useful for side branches, but does not address the main vessel.
As previously mentioned, emboli can become loosened during surgical endarterectomies and these emboli can have deleterious affects `downstream`. This occurrence would appear to be increased with a LIS approach due to the fact that in an open procedure, the site of revision is in direct view so that these particulate should be more easily detected Conversely in a LIS procedure the physician is dependent upon image intensification and his or her actual skill to not allow emboli from being dislodged and causing `downstream`, distal problems. U.S. Pat. No. 5,695,519, by Summers et al, describes a percutaneous filter for carotid angioplasty. This design disclosure appears to have merit, but by design, it has a membrane of filter material that is overlapping that increases its diameter prior to deployment and upon un-deployment. The present invention obviates this disadvantage of a larger diameter in that there are no overlapping filaments. Further, a cumbersome `gun` is required with the Summer system. Even further, the system is used only with angioplasty, which, as previously mentioned has a temporary effect. U.S. Pat. Nos. 4,842,579 and 4,926,858 describe distal barriers associated with atherectomy devices. Atherectomy has fallen from favor due to its apparent lack of efficacy combined with the complexity of use as compared with stent or stent-graft placement. Certainly, these devices have not been perfected nor attempted for use in the head in neck area. The filter/trap/occluder device of the present invention is designed to be used alone without any angioplasty, atherectomy device. Further, the present filter invention has been fabricated and tested where diameters of the device are as small as 0.010 inches in diameter. With sizes this small and smaller, use in the vasculature of the head, is now available. This area appears to be the new and large frontier in the treatment COD. Further, the filter/trap/occluder system of the present invention provides for a novel braiding technique (that is used in the bifurcated stent or stent-graft as well) that allows for entrapment of particles and removal.